I know that rest days are important, but I had a question about them: I started running today, but have been cycling fairly regularly. I ran 4.2 miles this evening, and quit there, because I didn't want to overdo it my first time out. Cardio-wise I'm fine (as I ride 70-100 miles/week right now), and there is a tingling in my calves and quads from using muscles in a way I haven't before.

My question is what will the ill effects of commuting tomorrow be? It is a 10 mile ride I do regularly and since I have only gotten out once this week I was kind of planning on it. Furthermore, I plan on trying to begin a Strava challenge on saturday that will entail riding about 30 miles per day for 2 weeks. The question isn't about the Strava challenge, as 30-odd miles isn't any sort of stress on my system that really requires recovery days, but just if you would recommend against riding tomorrow after starting running, or if I shouldn't have any serious problems forgoing a rest day just this once.

your legs will be sore tomorrow from running . Ive done the same thing many times . I run during the summer once every week (4-5 miles) to 10 days and legs are sore every time. I run 3-4 times a week in the winter and ride the bike 1-2 times a week as I live in new england

I woke up this morning and knew I wasn't riding. My legs were a bit sore, but more important my knees and ankles were in awful condition. Any sort of pivoting action was killer on my joints. By the end of the work day and trying to lay off of my legs and not walk too much my knees are much better. As far as running, I wan't to try to do it, but I won't be starting again until I am done with this challenge attempt in two weeks, (I am not trying to top the lists or anything, I just want to do it as a personal achievement) then I think I might on the days I don't bike (as long as my body isn't actively telling me not to rest) and got like that till the winter, and start lifting again. Hopefully by then I'll have lost 10-ish pounds, depending on who soon winter gets bad.